This invention relates to combustors for gas turbine engines, and in particular to wall elements for use in wall structures of combustors of gas turbine engines.
It is known to construct combustors of gas turbine engines with radially inner and outer double-walls, each having an external wall and an internal wall, the internal wall being formed of a plurality of tiles or other similar wall elements. Air is passed between the internal and external walls to provide cooling. Some of this air passes onto the hot side of the internal walls through effusion cooling holes to form a film of cooling air thereover.
The tiles typically overlap, often with a relatively cooler side of an upstream tile overlapping a hotter side of a downstream tile. This means that cooling air from the cooler side of the upstream tile can pass onto the hotter side of the downstream tile also to provide a cooling film.
Projections such as pedestals are generally provided on the rear of the tiles, extending toward the outer wall, to provide heat transfer. The pedestals are typically arranged in staggered rows to maximise heat transfer. Cooling of the tiles therefore takes place on the cooler side by convection from the projections and on the hotter side by film cooling.
Whereas these known tile configurations are sufficient to cool the tile, they use a significant amount of cooling airflow that could otherwise be used to improve propulsive efficiency of the engine. Furthermore, the pedestals cause turbulence in the cooling airflow exiting an upstream tile. This turbulence increases the amount of mixing of the film cooling air and the combustion products.
The object of the present invention is therefore to provide an improved cooling film across the surface of the downstream tile and thereby increasing the life of the tile.